Welded joint and method of making the same



UNITED STATES PATENT OFFICE WELDED JOINT AND METHOD OF MAKING THE SAME Russell Franks, Niagara Falls, N. Y., assignor, by mesne assignments, to Union Carbide & Carbon Corporation, a corporation of New York No Drawing. Application June 6, 1935, Serial No. 25,304

4 Claims. (Cl. 113-112) The invention is a method of welding and a Table A welded joint having new and useful properties.

Steels which contain about 2% to about 16% Analysis [mum chromium, appreciable amounts of carbon up to pact 3 m} about 0.5%, and in which the iron is in the f G Ch w 3 m number 5 5 ritic condition, harden when quenched or air cooled from elevated temperatures; but this prop- I erty may be substantially eliminated by adding to Z1 8;32 11 3 3; the steels at least about eight times, but not over 222 ga? l 3% g? thirty times, as much columbium as carbon. 6156 0106 1119 3,42 159 l0 0 Ferritic steels which contain about 16% to about 30% chromium and up to about 0.5% carbon are relatively hard in all conditions of heat treatment, are rather brittle when slowly cooled from elevated temperatures, and can be fully annealed only by holding at elevated temperatures for several hours and by subsequent rapid cooling. These higher chromium steels may be made softer and capable of more rapid annealing by the addition of at least about eight times, but not over 20 thirty times, as much columbium as carbon.

The above described chromium-columbium The beneficial efiects of suitable additions of tungsten upon the welding characteristics may conveniently be illustrated by the data in Table B. These data were obtained by welding the edges of steel plates inch thick, grinding off excess filler metal above the surfaces of the plates, cutting a coupon about 8 inches long and 2 inches wide, the welded joint being about in the center of the coupon and transverse to the longer 20 axis of the coupon, holding one end of the coupon steels, when heated at elevated temperatures such m heavy Vise bendmg the coupon with as are encountered, for example, during welding, blows appnee the free end of the coupon lose an appreciable proportion of the ductility and e Weld Just began to crack and toughness characteristic of the mechanically measurmg the apprexlmate angle of bemi In worked steels of the same composition. This phe- Table the angles of bend are given under the nomenon is apparently connected with the inheading Bendeesv'i underAaPPe9'rmean81ecrease in grain size at high temperatures but obtained on samples as welded, with no further many of the known expedients for decreasing the heeetreatmem whlle under are the angles 3 average grain size of steels fail to improve the Obtamed on Samples which after Welding, were ductility and toughness of the chromium-columheated 1 to 3 minutes at bollt (with bium steels at elevated temperatures. For exthe Weldmg torch) and the! a ample, the addition of about 1% of nickel or Table B copper greatly refines the grain size of the 35 chromium-columbium steels, but destroys their softness and ductility. Rod analysis Plate analysis Bend tests The present invention is based on the discovery that suitable additions of tungsten or molyb- 0 0b Cr 0 i A B 40 d'enum, or both, greatly refine the grain struc- 0 ture of these columbium bearing steels without- 6.15 0. 07 1.55 Nil 5.03 0 12 0.00 90: 160: 1y greatly increasing their hardness or destroy- 2 1; 8:8; 5:22 g2; 22,, 1 3,, ing their toughness. At least about 0.5% tung- 13.24 0.09 1.00 1.01 13.35 0.1: 0.535 180: n80: sten is required to secure substantial benefits, g; 8158 i 1; 28 H5 H8 fig. 3,3. and more than about 2.5% of this element de- 45 stroys the toughness of the steel. The preferred .weld did not mack 0 bend tungsten content is between about 1% and about 1.5%. If molybdenum is substituted for tungsten n mventlon may be ppl e t0 steels cont Should not exceed 2% taming from about 2% to about 30% chromium The necessity for limiting the amount of tung- P up to about 05% carbon; P 1t 18 0f pfi- 50 sten or molybdenum in these steels is demontlcularly great value when pp d osteels 00nstrated by the following data in Table A which in= taining about 4% to ab u Chromium d dicate the impact strengths of several st m in to about 0.30% carbon. Themetal of thearticles the rolled and heat-treated (fully softened) corn to be welded pr ly contain Sufficienttitanium ditlon: to decrease substantially the hardness and hardabout 1% excess titanium over this ratio of four) but this feature is not essential.

The weld filler material should have a columbium content at least eight times as great as the carbon content but not more than ten times the carbon content plus 1.5%. Preferably, the excess of columbium over ten times the carbon does not exceed about 0.75%.

I claim:

1. A strong and ductile welded joint comprising adjacent edges of at least two body portions and weld filler material between and uniting said adjacent edges, said body portions and filler material being composed of ferritic steel containing 2% to 30% chromium and up to 0.5% carbon, and said filler material containing substantially no unstable carbides which can be dissolved and reprecipitated in said material and containing columbium in an amount at least abouteight times, and not over about 1.5% plus ten times, the carbon content of said material,

, and about 0.5% to 2.5% 01' at least one metal of the group consisting of molybdenum and tungsten, remainder iron.

2. A strong and ductile welded joint comprising adjacent edges of at least two body portions and weld filler material between and uniting said adjacent edges, said body portions and filler material being composed of ferritic steel containing 4% to 20% chromium and up to 0.3% carbon, and said filler material containing substantially no unstable carbides which can be dissolved and reprecipitated in said material and containing columbium in an amount at least about eight times, and not over about 0.75% plus ten times, the carbon content of said material, and about 0.5% to 1.5% of at least one metal of the group consisting of molybdenum and tungsten, remainder iron.

3. A method of uniting adjacent edges of ferritic chromium steel articles containing about 2% to 30% chromium and up to about 0.5% carbon, by depositing between said edges molten weld filler metal composed of territic steel containing about 2% to 30% chromium and up to about 0.5% carbon, remainder iron, which method comprises introducing into said molten weld filler material about 0.5% to 2.5% of at least one metal of the group consisting of tungsten and molybdenum, and columbium in an amount at least about eight times, and not over 1.5% plus ten times, the carbon content oi said weld filler material; said columbium being eflective to prevent the existence in said filler material of any substantial amount of unstable carbides which could be dissolved and reprecipitated in said material.

4. A method of uniting adjacent edges of ferritic chromium steel articles containing about 4% to 20% chromium and up to about 0.3% carbon, by depositing between said edges molten weld filler metal composed of ferritic steel containing about 4% to 20% chromium and up to about 0.3% carbon, remainder iron, which method comprises introducing into said molten weld filler material about 0.5% to 1.5% of at least one metal of the group consisting of tungsten and molybdenum, and columbium in an amount at least about eight times, and not over 0.75% plus ten times, the carbon content of said weld filler material; said columbium being eil'ective to prevent the existence in said filler material of any substantial amount of unstable carbides which could be dissolved and reprecipitated in said material.

RUSSELL FRANKS. 

